Subaru IMPREZA GD 2007 Series Manual page 214

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Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of air flow sensor signal using
the Subaru Select Monitor or general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to
"READ CURRENT DATA FOR ENGINE". <Ref.
to EN(H4SO)(diag)-32, Subaru Select Monitor.>
• General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
2 CHECK POWER SUPPLY OF MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the mass air
flow and intake air temperature sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between mass air flow
and intake air temperature sensor connector
and engine ground.
Connector & terminal
(B3) No. 1 (+) — Engine ground (–):
3 CHECK HARNESS BETWEEN ECM AND
THE MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR CONNECTORS.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM.
3) Measure the resistance of harness between
ECM and mass air flow and intake air tempera-
ture sensor connectors.
Connector & terminal
(B135) No. 26 — (B3) No. 3:
4 CHECK HARNESS BETWEEN ECM AND
THE MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR CONNECTORS.
Measure the resistance between ECM and
chassis ground.
Connector & terminal
(B135) No. 26 — Chassis ground:
5 CHECK POOR CONTACT.
Check for any poor contact between the ECM
and the mass air flow and intake air temperature
sensor connectors.
Check
Is the voltage less than 0.2 V? Go to step 2.
Is the voltage 10 V or more?
Is the resistance less than 1 Ω? Go to step 4.
Is the resistance 1 MΩ or
more?
Is there poor contact in the
ECM or the mass air flow and
intake air temperature sensor
connectors?
EN(H4SO)(diag)-105
ENGINE (DIAGNOSTICS)
Yes No
Even if the malfunc-
tion indicator light
illuminates, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the fault con-
dition, and
reperform the
check.
NOTE:
In this case, there
may be a tempo-
rary connector
contact failure.
Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
main relay and
mass air flow and
intake air tempera-
ture sensor con-
nectors.
• Poor contact of
main relay connec-
tor
Repair the open
circuit of harness
between the ECM
and mass air flow
and intake air tem-
perature sensor
connectors.
Go to step 5.
Repair short cir-
cuit of the harness
to ground between
the ECM and the
mass air flow and
intake air tempera-
ture sensor con-
nectors.
Repair any poor Replace the mass
contact between air flow and intake
the ECM and the air temperature
mass air flow and sensor. <Ref. to
intake air tempera- FU(H4SO)-28,
ture sensor con- Mass Air Flow and
nectors. Intake Air Temper-
ature Sensor.>